<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style type="text/css">
		/* 
派生选择器
   是由id选择器，class选择器，标签名选择器组合而成
	优先级     id>class>标签名	
例如  #box1 .span1>#box1 span> #box1>.span


		 */
#box1 span{

	border:  1px solid red;
}
#box2 span{
	display: inline-block;
	background: yellow;
	width: 100px;
	height: 100px;
}
	</style>

</head>
<body>
	<div id="box1">
		<span class="span1">我是box1的span</span>
		<span>我是box1的span</span>
		<span>我是box1的span</span>
		<span>我是box1的span</span>

	</div>
	<div id="box2">
		<span>我是box2的span</span>
		<span>我是box2的span</span>
		<span>我是box2的span</span>
		<span>我是box2的span</span>
	</div>
</body>
</html>